As a result of the stringent enforcement of this law in Wales, Casualty - which is filmed in Cardiff - had been forced to abandon the upcoming plotline.

Clare Hudson, head of productions at BBC Wales, made the revelation while addressing the Welsh national assembly on Tuesday. She claimed that the smoking ban could potentially cost the economy up to £20m a year, reports The Guardian.

Hudson told MPs: "We had one storyline in Casualty warning about the dangers of smoking and how it caused a fire in a hotel... but we could not go ahead with it because of the current legislation.

"And scenes in [the revamped] Upstairs, Downstairs were difficult to work around because we had to shoot them outside of Wales.

"Our drama in Wales has been growing very steadily over the past few years. We don't want to see that growth capped on the basis of the current legislation."

Hudson also revealed that the ban meant programme-makers have been forced to cross the border into England to film smoking scenes in Bristol, at the expense of an extra £5,000 a day.

Doctor Who, Sherlock, and Gavin & Stacey, three of the BBC's biggest hits in recent years, are all produced by BBC Wales and filmed in the country.

Mark Drakeford, a Labour member of the national assembly, rejected the call to overturn the ban, saying that it was "morally repugnant" to relax the rules just because different legislation applied in England.
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